Development of low- lossAg-sheathed superconducting tapes based on electromagnetic design and their application to AC power cables

从2005年度到2007年度，对基于电磁设计的低损耗Ag包覆超导带材的开发及其在交流电力电缆中的应用进行了3年的研究。（1）交流损耗测量系统的构建我们搭建了交流损耗测量系统，测量了超导带材在交流工作状态下，通过交流传输电流和任意方向的交流外磁场到达带材表面时产生的交流损耗。由此，能够求出在改变频率、输送电流振幅和磁场振幅的同时，通过带材和/或线材中的交流输送损耗和交流磁化损耗的合计而得到的交流损耗的合计值。(1)带阻障层的Ag包覆高温超导带材的制备与表征我们成功地制备了带阻障层的Ag包覆高温超导带材 ...更多信息 并研究了它们在电力电缆应用中的电磁性能。我们使用了两种方法来在磁带制造banier引入。一种是使用阻障膏的涂覆方法，另一种是使用具有良好机械性能的金属的内氧化方法。特别是使用Ca_2CuO_3粉末和30wt%Bi_（2212）粉末的混合物作为阻挡材料的带材制造产生了大约几米长的Ag护套带材，其具有相当好的和均匀的J_i（77 K，OT）分布，远高于10^4A/cm ~ 2（最大1.8 × 10^4A/cm ~ 2）。此外，这种势垒的引入引起横向磁阻的几倍增强，并且与未引入势垒的带相比，降低了高达1/3的交流损耗。(2)基于电磁场理论，对银包超导带材组成的圆柱形导体电缆附近的电场分布进行了研究，对交流损耗测量的误差估计起到了重要作用。在AC操作下的电场示出了取决于电缆结构的电缆附近的复杂变化，并且在离开带表面大约带宽度时，电场变得几乎恒定。结果表明，电缆导体的交流损耗测量应在距绝缘带表面至少为绝缘带宽度的距离处进行

Studies on development of low-loss Ag-sheathed superconducting tapes based on electromagnetic design and their application to AC power cables have been conducted for three years between fiscal 2005 and 2007. Main results through the study am summarized as follows:(1) Construction of AC loss measurement systemWe constructed the measuring system to obtain the AC losses generating in superconducting tape under AC operation, in passing through AC transport current and AC external magnetic fields at arbitrary directions to tape surface. Using this, we can obtain total values of AC losses obtained by a sum of AC transport losses and AC magnetization losses in the tapes and/or wires, while changing frequency, transport current amplitude and magnetic field amplitude.(1) Fabrication and characterization of Ag-sheathed high-Tc superconductiong tapes with interfilamentary resistive barriersWe successfully fabricated Ag-sheathed high-Tc superconducting tapes with interflamaaary resistive barriers … More and investigated their electromagnetic properties toward applications to electric power cables. We used two methods for banier introduction in tape fabrication. The one is the coating method using paste of resistive barriers and another the inner oxidization method using metals with nice mechanical properties. In particular the tape fabrication using mixture of Ca_2CuO_3 powder and 30 wt%Bi2212 powder as barrier materials produces Ag-sheathed tapes on the order of several meter lengths, which have considerable nice and homogeneous J,(77K, OT) distribution well above 10^4 A/cm2 (1.8 x 10^4A/cm2 at maximum). In addition, this barrier introduction causes several-times enhancement in transverse resistively and lowers the AC losses up to 1/3 compared to the tapes without barrier introduction.(2) Electric fields andAC losses for cylindrical conductor cables composed of Ag-sheathed superconducting tapesWe elucidate the electric-field distribution near cylindrical conductor cables composed of Ag-sheathed superconducting tapes based on the electromagnetic theory, which plays an important role in the error estimation for AC losses from measurements. The electric field under AC operation shows complicated variations in the vicinity of cables depending upon the cable structures and it becomes nearly constant in going away from the tape surface by about tape width. The result shows that AC loss measurements for cable conductors should be made at the distance far from the tape surface by at least tape width Less